Back in the summer of 2009, USB-connected D/A processors that could operate at sample rates greater than 48kHz were rare. Ayre Acoustics had just released its groundbreaking QB-9, one of the first DACs to use Gordon Rankin's Streamlength code for Texas Instruments' TAS1020 USB 1.1 receiver chip. Streamlength allowed the chip to operate in the sonically beneficial asynchronous mode, where the PC sourcing the audio data is slaved to the DAC. But high-performance, USB-connected DACs like the Ayre were also relatively expensive back then, so in the January 2010 issue of Stereophile I reviewed a pair of soundcards from major computer manufacturer ASUS , the Xonar Essence ST and STX, which, at $200, offered a much more cost-effective means of playing hi-rez files on a PC.

No, the $399 price listed in the specification block isn't a misprint. And yes, the Audio Alchemy Digital Decoding Engine v1.0 is indeed a full-function outboard digital processor. And since this is the August issue, not April, you can stop worrying that this review is some kind of joke.

With the introduction of Audio Alchemy's Digital Transmission Interface (DTI) more than three years ago, the company created an entirely new category of hi-fi product: the jitter filter. The original DTI was a good start, but didn't always improve the sound of the better-quality digital front-ends.

I don't know much about horses, but I've been given to understand that dead ones don't respond to even the severest beating. In light of that, I'll make only this brief statementEven with the best playback gear of my experience, I don't derive as much pleasure from CDs as I do from LPs.and move on to a simpler truth: Regardless of what I think, CD players are still a necessity for most music-loving audiophiles.

The past 12 months have seen some remarkable developments in digital playback. Standards of digital musicality are far higher than they were a year ago, both on an absolute performance basis and in terms of what you get at various price levels. No other component category has seen such tremendous gains in value for money or number of new products introduced. It seems hard to believe that since Vol.13 No.6 (12 issues ago), we've reviewed such noteworthy digital processors as the Meridian 203, Proceed PDP 2, Stax DAC-X1t, Theta DSPro Basic, Wadia X-32, Esoteric D-2, PS Audio SuperLink, and VTL D/A. Each of these converters brought a new level of performance to its price pointor, in the case of the Stax and VTL, established a new benchmark of ultimate digital performance.

Just as these units provided stiff competition for previous products, so too will they come under the assault of improving technology. The art of digital processor design is so young that we can continue to expect further improvements coupled with lower prices as designers move up the learning curve.

Now entering its fourth decade, the Compact Disc player seems to have reached a stage of maturity where the best models within a given price range will sound pretty much alike. The technology of the Compact Disc itself is set, its possibilities and limitations are well understood; and the designers of CD players who figure out how to stretch the former and finesse the latter wind up at about the same sonic place (again, for the same price), even if they've taken different routes to get there.

Unless something is broken, the bits from your computer will be delivered to your DAC intact; the claim behind three new products I recently listened through is that each can reduce noise within the DACnoise that could otherwise corrupt the analog signal and thus make our music less musical. This notion is not based on audiophool woo-woo, but on the basic electronics of mixed-signal systems: Although its input is digital data, a DAC's output is subject to all the noise problems of analog circuits.

Approximately 331/3 years after AudioQuest's first phono cartridge, the company announced two new USB D/A headphone amplifiers: the DragonFly Black ($99) and the DragonFly Red ($199). Both have circuits designed by the engineer responsible for the original DragonFlyGordon Rankin, of Wavelength Audioand both have the novel distinction of requiring considerably less operating power than their predecessors, so much less that the new DragonFlys can be used with iPhones, iPads, and various other mobile devices.

Thus spoke AudioQuest's Steve Silberman, VP of development, of their brand-new USB D/A converter, the DragonFly. "There are a lot of very good DACs out there," he continued. "There are even a lot of very good affordable DACs. But the problem is, people outside of audio don't want them: They don't want old-style components like that.

I got an early start on computer audio. At the end of the last century I was using WinAmp with first a CardDeluxe PCI soundcard, then a similar card from RME, to play files on a Windows PC. After I became a MacPerson, I used FireWire audio interfaces from pro-audio company Metric Halo and an inexpensive USB-connected ADC/DAC from M-Audio. But it was with the USB version of Benchmark's DAC 1 that the computer began taking over from physical discs for my music listening. At first I used iTunes au naturel, but as I acquired more high-resolution files, I began using Pure Music to handle all the tedious audio housekeeping, assigning as a dedicated music server a G4 Mac mini I'd bought in 2006.

I eat bits for breakfast. Lunch is a simple bit-sized snack. And dinner is the analog to real food. This has been my routine these past four years as editor of AudioStream.com, where we digest all things computer audio.

In that time I've reviewed over 100 digital-to-analog converters, ranging in price from $60 to over $12,000. This adds up to roughly 150,000 words spilled on DACs. You'd think my pen would be running dryespecially if you feel, as some do, that all DACs sound pretty much the same. If that were the case, I could have written just one review, for that very first DAC, then cut and pasted it for all the rest. What was I thinking?

I was alerted to the new VEGA D/A processor from Chinese manufacturer AURALiC by Michael Lavorgna's rave review for our sister site AudioStream.com in April 2013: "Everything I played through the Auralic Vega was equally wow-inducing. Everything. . . . Music I've heard hundreds of times was presented with a crisp, clean, and delicate clarity that was simply uncanny and made things old, new again. . . . Its ability to turn music reproduction into an engaging and thrilling musical experience is simply stunning."

Aurender was a name new to me when I encountered the company at the 2015 Consumer Electronics Show, where they displayed a range of music servers designed in California and manufactured in South Korea. But what caught my attention in Aurender's suite was their Flow portable D/A headphone amplifier ($1295). This handsome, battery-powered device, housed in a machined aluminum case about twice the size of a pack of playing cards, offers optical S/PDIF and USB 2.0/3.0 input ports and a single ¼" stereo headphone jack. Two features distinguish the Flow from the pack: Its USB input can be used with iOS (iPhone/iPad) and Android smartphone sources, and it can accept an mSATA drive (not included in price) of up to 1TB capacity for internal storage of audio files. Visually, the Flow's distinguishing feature is its round LCD display, which stands proud of the faceplate; the bezel encircling the display acts as a velocity-sensitive volume control operating in 0.5dB steps.

I first spied the Ayre Codex two Januarys ago, at the 2015 Consumer Electronics Show, and its scrappy proletarian vibe sure made it look different from any other Ayre creation. On learning that its price would be well under $2000, I was immediately curious what Charley Hansen and his gangmakers of the $3450 QB-9DSD USB digital-to-analog converter, plus a few five-figure amps and preampscould create when cost is an object.

Since its founding in 1993, Colorado-based Ayre Acoustics has made its name with amplifiers and preamplifiers based on truly balanced, solid-state circuitry that didn't use the ubiquitous panacea of loop negative feedback to produce linear behavior. Their first digital product was the D-1x DVD player, reviewed for Stereophile by Paul Bolin in February 2003, which offered unusually good video performance. The D-1x was followed by the C-5xe and DX-5 universal players, respectively reviewed by Wes Phillips (July 2005) and Michael Fremer (December 2010). But the most intriguing digital product to come from Ayre was the QB-9 digital processor. Reviewed by WP in October 2009, the QB-9 has just one input, USB, and uses Gordon Rankin's proprietary Streamlength code to give asynchronous operation, which in theory offers the best jitter suppression. "The QB-9 isn't a computer peripheral," said Ayre's marketing manager at that time, Steve Silberman. "It makes computers real high-end music sources"a statement with which WP agreed.